Fertilizers are responsible for over half of global food production, but there are areas in world with nutrient deficiency and other areas of nutrient excess.
Managing mineral plant nutrients requires careful application of science and skill to meet production, environmental, and social goals.

Monday, May 6, 2013

Compound Fertilizer: Mixing several nutrients in each granule

Compound fertilizers contain
several nutrients in each granule

Many soils require the addition of several essential nutrients to
alleviate plant deficiencies. Farmers may have the option of selecting a
combination of single-nutrient fertilizers or using a fertilizer that has
several nutrients combined into each particle. These combination (compound or
complex) fertilizers can offer advantages of convenience in the field, economic
savings, and ease in meeting crop nutritional needs.

Production

Compound fertilizers are made using basic fertilizer materials, such as
NH3, ammonium
phosphate, urea, S, and K salts. There are many methods used for making these
fertilizers, with the specific manufacturing processes determined by the
available basic compo­nents and the desired nutrient content of the finished
product. Here are four brief examples.

Compactionmethods
(agglomeration) involve binding small fertilizer particles together using
compaction, a cementing agent, or a chemical bond. Various nutrient ratios can
be combined using undersized particles that may not be suitable for other
applications.

Accretion-basedfertilizers are
made by repeatedly adding a thin film of nutrient slurry which is continually
dried, building up mul­tiple layers until the desired granule size is reached.

Pipe-cross reactorsare used to
chemically melt NH3, acids containing
S or P, and other nutrients—such as K sources and micronutrients—into a solid
fertilizer with the desired nutri­ent content.

The nitrophosphate processinvolves reacting
phosphate rock with nitric acid to form a mixture of compounds containing N and
P. If a K source is added during the process, a solid fertilizer with N, P, and
K will result.

Compound fertilizer contains multiple nutrients in each individual
granule. This differs from a blend of fertilizers mixed together to achieve a
desired average nutrient composition. This difference allows compound
fertilizer to be spread so that each granule delivers a mixture of nutrients as
it dissolves in the soil and eliminates the potential for segregation of
nutrient sources during transport or application. A uniform distribution of
micronutrients throughout the rootzone can be achieved when included in
compound fertilizers.

These fertilizers are especially effective for applying an initial
nutrient dose in advance of planting. There are certain ratios of nutrients
available from a fertilizer dealer for specific soil and crop conditions. This
approach offers advantages of simplicity in making complex fertilizer
decisions, but does not allow the flexibility to blend fertilizers to meet
specific crop requirements. Turf managers and homeowners often find compound
fertilizers desirable.

Management
Practices

Compound fertilizers are sometimes more expensive than a physical
combination or blend of the primary nutrient sources since they require
additional processing. However, when a consideration is made of all the factors
involved with nutrient handling and use, compound fertilizers may offer
considerable advantages.

Nitrogen is the nutrient that most commonly needs to be carefully
managed and reapplied during the growing season. It may not be feasible to
supply sufficient N in advance of planting to meet the entire demand (using
only compound fertilizer) without overapplying some of the other nutrients. It
may be advisable to use a compound fertilizer early in the growing season and
then later apply only N fertilizer as needed.

Compound fertilizers are usually produced regionally
to meet local crop needs. There is a wide range of chemical and physical
properties that can be adjusted to meet these needs. For example, a desire to
minimize P in urban stormwater runoff has led some communities to restrict the
addition of P to compound fertilizers sold for turf and ornamen­tal purposes.
Soils of a region that are typically low in a specific nutrient may have this
element boosted in the compound fertilizer.

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About Me

I am a soil scientist with interest in managing plant nutrients in the best way possible. I am fortunate to be able to work in research and education to be able to accomplish this goal.
After receiving a PhD in Soil Science at the University of California (Riverside), I worked as a Research Scientist for the U.S. government, as a Professor of Soil Science, and now I work for a not-for-profit institution. It's been a wonderful experience!